This invention relates generally to apparatuses for reproducing rotary recording mediums, and more particularly to improvements in an apparatus wherein a rotary recording medium such as a record disc is drawn against a rotary structure such as a turntable sheet or a turntable, on which the record disc is placed, thus making it possible to carrying out the reproducing operation in a highly satisfactory manner.
Heretofore, in apparatuses for reproducing rotary recording mediums such as the record discs, the record disc to be reproduced has been merely placed on a turntable. In such apparatuses, therefore, if the record disc is warped, it will rotate in a warped state, and will not closely contact the turntable (a state referred to as "poor adherence"). When the record disc rotates in a warped state, the pickup arm (tone arm) is adversely caused to swing in the vertically following the warp of the record disc. As the pickup arm swings, the reproducing stylus in the pickup cartridge of the pickup arm is displaced in the longitudinal direction of the sound groove. Accordingly, the reproduced signal is subject to frequency modulation, thus developing wow. Furthermore, warping of the record disc causes the cantilever to undergo rotational displacement beyond the normal range. Accordingly, the moving magnet or the like adopted to undergo vibratile motion in accordance with the signal recorded in the sound groove is also displaced beyond the normal range with a resulting loss in the linearity of power generating efficiency. As a consequence, amplitude modulation and distortion are produced.
Moreover, if the record disc adheres poorly to the turntable, sound from the speaker units will be fed back to the record disc in an acoustic manner and the resulting howling phenomenon will deteriorate the quality of the reproduced sound.
Furthermore, in a rotary recording medium such as a video disc, warping causes fluctuations in the state of contact between the reproducing stylus and the rotary recording medium, thus impairing satisfactory reproduction.
Accordingly, there have been proposed apparatuses for maintaining the record disc in close contact with the turntable so as to eliminate the above described difficulties. In one such apparatus, the warp is eliminated from the record disc and the record disc is kept in close contact with the turntable either by placing a weight on the record disc at the center thereof or alternatively by depressing the peripheral portion of the record disc by means of a ring member. However, this apparatus gives rise to difficulties in that the warping of the record disc cannot be corrected completely and that the manual operations involved are rather troublesome. Moreover, in another such apparatus, a sheet on the turntable is adopted to undergo deformation in conformance with warp of the record disc placed thereon. This apparatus, however, has a shortcoming in that the warp of record disc cannot be corrected so that wow and distortion cannot be eliminated.